Mechanical Grandfather Clock

I designed a mechanical grandfather clock for my long-term project. I came up with the idea over the summer while trying to think of a project that would not only be practical/usable but also not involve any electronics. I designed the basics of the project based simply on the image above and somehow got it to work really well

1.75 mm hyper PLA filament

Creality K1 Max Printer

ball bearings x11

Fusion 360 spur gear add-on

Creality print slicer software

10-24 3" machine screws x8

10-24 nuts x8

6ft 2x12 redwood

https://www.youtube.com/watch?v=yow5ZHcfQaY

Using the linked video above, I began my project by designing the deadbeat escapement mechanism. This video is not the best, but it helped me learn the basics and model the basic shape, which I gradually modified throughout the project to fit the bearing better and prevent slipping/sticking. I did the same thing with the escape tooth gear which the drawing is in the pdf below with all the dimensions. Ultimately I ended up attaching this escapement gear to another gear which contributed to the gear ratio of both the hour and minute hands. The fusion model of the final design including the gear ratio and housing is included below.

The original prototype consisted of just the escapement. This design helped with getting the press fits down between the gear, the anchor, and the bearing, as well as the bearing into the housing. It wasn't functional yet, but it served as a good fidget toy. Completed the basic motion of the escapement.

I redesigned the anchor to have a spot for a pendulum to attach in the back and added a spot to wrap the driving weight around the escapement gear. 3d printing the escapement gear was a little difficult due to overhangs, which wasn't something I fixed till later, when I began using metal shafts to increase stability. These print errors caused the string to get stuck and prevented the weight from pulling on the gear. The gear not being supported on both sides was also an issue, as it would pull the gear downwards at an angl,e making it more difficult to spin and causing skips

After my previous prototype, I began working on gear housings for the gear ratio. My first goal was to make the 1:60 ratio for the minute hand. I designed the box in Fusion and decided to cut it out of wood on the router to save filament. This ended up with the box not fitting together well. The gears I designed originally also did not fit onto shafts that fit well in the bearing, so I had to use painters' tape in order to make the fit better. This led to the gears being off kilter and would stop them from spinning. In order not to have to use the painters' tape anymore in an attempt to make things spin straighter and just to be overall cleaner, I machined shafts that threaded together on either side of the hole in the gear. This also helped the gear maintain a specific distance along the shaft. In the end, this did not end up working because of loose-fitting tolerances and just overcomplicating things. Another major issue with this design is the shafts aren't supported on both sides causing flex and making the loose tolerances of the shafts even more noticeable.

My next design included fully 3D-printed parts as well as a pre-machined shaft taken from a printer press, fitted through the center hole of the gears. I got pretty lucky to find a shaft of the exact size I needed, but depending on the size of your bearings, you can machine the shafts yourself or buy some in the size you need. To do this, you can adjust the size of the center hole of the spur gears until it's a press fit. The size of the center hole in my gears is slightly smaller than that of the middle of the ball bearings. In the new 3D-printed gear housing, I designed the gears to be supported on both sides by bearings, and the housing is just wide enough to prevent the gears from moving farther away from each other. All of the gears have a through hole through the center. A major upgrade over the previous design is the support for the shafts on both sides to prevent flex; this ended up being a major, and I would argue necessary, addition.

To have a functional hour hand gear ratio, I attached this back housing plate. This housing supports the 3d printed gears on both sides, which provide a 12:1 ratio. The smallest gear at the top is attached to the same shaft as the last gear in the 1:60 gear ratio. It's fixtured to the main housing in the same way the other is fixed to itself.

For manufacturing, I 3D printed all the components on a Creality K1 MAX printer. I took all of my designs from Fusion and put them through the Creality print slicer software. To do so, you go into fusion, select the models you want to 3d print, go into the far right folder at the top, select 3d print, then in Creality, click upload file, then select your model. For the shafts, I cut multiple lengths of a pre-machined shaft taken out of a printer. Everything on the inside of the clock, including the gears on the shafts and the ball bearings to the housing, is attached with a press fit. The tolerance for your press fits can depend on the elasticity of your prints as well as other variables. My tolerances were around 5x10^-3 inches. I've been unable to manufacture the wood portion of my clock, I planned on machining it on the router out of a piece of 2"x12"x8' redwood I bought from the lumber yard. If I were to machine it I would cut it down to around 6 ft and use the cam linked earlier in this Instructable to emboss the face of the clock and drill holes where the hands would go.

Gears are hammered onto their respective shafts (shaft length is lenient but has to be long enough to go through both holes or for the one shaft serving as the minute hand to connect to the second gear ration that runs the hour hand. The base plates are connected with 10-24 x 2" machine screws hammered through the holes in the corners. In the current design the driving weight must be wrapped around the escapement gear before assembly as the escapement won't spin the opposite direction. This is a design flaw since the clock must be disassembled in order to rewind it.